The invention relates to a method of reversably storing hydrogen and to a hydrogen reservoir.
The storage of hydrogen is a problem particularly when hydrogen is to be used as an energy source and energy transport medium. Hydrogen can easily be manufactured by the electrolysis of water for example using electricity generated by solar cells. The energy stored in the form of hydrogen can then be recuperated by combustion of the hydrogen, but it can also be converted directly into electrical energy by way of fuel cells. However, the problem of storing the hydrogen, especially small amounts and particularly for mobile applications (fuel cell cars), has not been satisfactorily solved so far.
Since the conventional storage materials for storing hydrogen are not satisfactory, particularly for future applications, improved concepts and materials are urgently needed. Many materials have already been manufactured for that purpose and have been tested in various temperature and pressure ranges. It is however desirable to have, in addition to the material composition, the pressure and the temperature, other variables which could change the hydrogen storage properties of a hydrogen reservoir or a hydrogen storage material.
Conventional storage arrangements require expensive auxiliary components such as compressors for operating the hydrogen pressure reservoirs. In cryo storage arrangements, the infrastructure requirements are particularly high since special cooling equipment for very low temperatures of −253° C. (20° K) is required. The storage system transfer lines and tank couplings must be super-insulated in order to avoid fast and premature evaporation of the liquid hydrogen. A disadvantage of the metal hydride storage devices is that, depending on the alloy, for the release of the hydrogen either high temperatures or additional pumps are required. Chemical storage devices require reformers, which must be heated and/or an expensive regeneration of the storage devices.
The construction and the operation of the auxiliary equipment requires energy, occupies space, which may be critical with mobile applications, and is expensive. In some cases, for example with reformers or apparatus, which must be heated to relatively high temperatures, the response time may present a problem.
Although electrolysis apparatus can be used for the production of hydrogen, they require large amounts of energy. They are therefore economically not feasible as hydrogen, that is, energy suppliers in the sense of a hydrogen economy.
It is the object of the present invention to provide a method and an apparatus for storing hydrogen for use as energy source wherein the hydrogen is released at relatively low temperatures.